1. Field
The present disclosure relates to a composite cathode active material, a lithium battery including the composite cathode active material, and a method of manufacturing the composite cathode active material, and more particularly, to a composite cathode active material with improved charge/discharge rate characteristics and improved lifetime characteristics, a lithium battery including the composite cathode active material.
2. Description of the Related Art
A lithium battery, more specifically a lithium ion battery, has been used as a power source for many portable devices due to its high energy density and easiness in its design. Recently, as the lithium ion battery has been also adopted as a power source for electric vehicles or for power storage in addition to a power source for portable information technology devices, research has been intensely focused on the study of a lithium ion battery with high energy density and a long lifetime.
Among them, a method of coating a cathode surface of the lithium ion battery by using a coating material has been considered a method to greatly improve the function of the lithium ion battery by modifying a cathode active material of the lithium ion battery based on an available cathode active material.
A coating material that is used in the coating method includes an electrochemically stable oxide or a phosphate. The coating material blocks direct contact between a cathode surface and an electrolyte. As a result, the coating material prevents ion elution caused by the direct contact between a cathode surface and an electrolyte, and also the dissolution of oxygen ions in the cathode oxide, thereby improving structural stability and thermostability of the cathode active material.
However, the method of coating the cathode surface with a coating material, such as an electrochemically stable oxide or a phosphate, can cause a decrease in specific capacity due to the use of the coating material not directly involved in the charge/discharge reaction. Additionally, the coating can decrease an active reaction area, thereby increasing interfacial resistance while deteriorating high rate charge/discharge characteristics.
Furthermore, with the recent increasing demand for a high energy density cathode active material, the study on a high-voltage cathode active material is also on the increase. Accordingly, it would be desirable to develop a coating material which prevents the oxidation of an electrolyte on the surface of the high-voltage cathode active material, and also prevents the deterioration in the conductivity of the high-voltage cathode active material.
Therefore, there still remains a demand for a cathode active material with improved charge/discharge rate characteristics and improved lifetime characteristics at a high voltage, a lithium battery including the cathode active material, and a method of manufacturing the cathode active material.